U.S. patent number 6,767,983 [Application Number 09/937,598] was granted by the patent office on 2004-07-27 for silicone resin and photosensitive resin composition containing the same.
This patent grant is currently assigned to Nippon Steel Chemical Co., Ltd.. Invention is credited to Takeshi Fujiyama, Takero Teramoto.
United States Patent |
6,767,983 |
Fujiyama , et al. |
July 27, 2004 |
Silicone resin and photosensitive resin composition containing the
same
Abstract
This invention relates to photosensitive silicone resins and
resin compositions containing the same. Silicone resins of this
invention are characterized by that a triorganosilyl group
represented by the following general formula (1) ##STR1## wherein R
is a divalent organic group and R' is a divalent group or a direct
bond is linked to all or a part of the ends of the backbone of
polyorganosilsesquioxanes. Photosensitive resin compositions of
this invention are formulated from the aforementioned silicone
resins and a photogenerator of acid. The aforementioned silicone
resins and photosensitive resin compositions show excellent
performance as resist materials for multi-level resist processes
and for forming barriers of PDP and, on account of their excellent
plasma resistance (resistance to O.sub.2 -RIE), yield patterns of a
high aspect ratio.
Inventors: |
Fujiyama; Takeshi (Kisarazu,
JP), Teramoto; Takero (Tokyo, JP) |
Assignee: |
Nippon Steel Chemical Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
13970778 |
Appl.
No.: |
09/937,598 |
Filed: |
September 28, 2001 |
PCT
Filed: |
March 29, 2000 |
PCT No.: |
PCT/JP00/01955 |
PCT
Pub. No.: |
WO00/59987 |
PCT
Pub. Date: |
October 12, 2000 |
Foreign Application Priority Data
|
|
|
|
|
Mar 30, 1999 [JP] |
|
|
11-089441 |
|
Current U.S.
Class: |
528/26; 525/474;
528/12; 528/33; 528/41 |
Current CPC
Class: |
C08G
77/04 (20130101); C08G 77/045 (20130101); C08G
77/14 (20130101); C08G 77/38 (20130101); C08L
83/06 (20130101); C08L 83/14 (20130101) |
Current International
Class: |
C08G
77/00 (20060101); C08G 77/38 (20060101); C08G
077/14 (); C08G 077/04 () |
Field of
Search: |
;528/12,26,33,41
;525/474 ;252/582 ;430/270.1,272.1 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
5385804 |
January 1995 |
Premlatha et al. |
5612170 |
March 1997 |
Takemura et al. |
6210856 |
April 2001 |
Lin et al. |
6284858 |
September 2001 |
Fujiyama et al. |
6303268 |
October 2001 |
Namba et al. |
6309796 |
October 2001 |
Nakashima et al. |
|
Foreign Patent Documents
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|
|
|
|
|
|
A11-60734 |
|
Mar 1999 |
|
JP |
|
A9/841566 |
|
Sep 1998 |
|
WO |
|
Other References
English Abstract of JP 06-027671, Feb. 1994, Sachdev et al.* .
English Abstract of JP 06-095385, Apr. 1994, Premlatha et al.*
.
English Abstract of JP 06-248082, Sep. 1994, Lagarde et al.* .
English Abstract of JP 06-329687, Nov. 1994, Freyer et al.* .
English Abstract of JP 07-056354, Mar. 1995, Iwasa et al.* .
English Abstract of JP 08-193167, Jul. 1996, Sakata.* .
English Abstract of JP 10-062981, Mar. 1998, Kosaka et al.* .
English Abstract of JP 10-251407, Sep. 1998, Fujiyama et
al..
|
Primary Examiner: Robertson; Jeffrey B.
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Parent Case Text
This application is the national phase under 35 U.S.C. .sctn. 371
of PCT International Application No. PCT/JP00/01955 which has an
International filing date of Mar. 29, 2000, which designated the
United States of America.
Claims
What is claimed is:
1. Silicone resins wherein a triorganosilyl group represented by
the following general formula (1) ##STR4##
wherein R is a divalent organic group and R' is a divalent group or
a direct bond is linked to all or a part of the ends of the
backbone chain of polyorganosilsesquioxanes.
2. Silicone resins as described in claim 1 wherein the
polyorganosilsesquioxanes contain a repeating unit represented by
the following general formula (2) ##STR5##
wherein R.sub.2 is an unsubstituted or subsituted phenyl group and
the average number of repeating units is 2-5,000.
3. Silicone resins as described in claim 1 wherein the
polyorganosilsesquioxanes consist of one type or a mixture of two
types or more seleted from ladder type, cage type, and mixed
cage-ladder type and their weight average molecular weight Mw
determined by gel permeation chromatography (GPC) and calibrated
against polystyrene is 800-100,000.
Description
FIELD OF TECHNOLOGY
This invention relates to silicone resins and photosensitive resin
compositions containing the same useful as resist materials.
BACKGROUND TECHNOLOGY
In the fields of a variety of electronic devices including
semiconductor devices that require microfabrication, there is a
rising demand for higher density and higher degree of integration
of devices and finer patterning has become essential to meet this
demand. Moreover, in plasma display panels (PDP), barriers of a
high aspect ratio, that is, a high ratio of height to width, are in
demand in order to have light of high luminance emitted by
enlarging the electric discharge space for display.
A method for obtaining higher resolution in patterning is to use
light of shorter wavelength in patterning of photoresists. However,
the use of shorter wavelength poses a problem of the depth of focus
(DOF) becoming reduced with a drop in sensitivity and aspect ratio.
Multi-level resist processes have been proposed to solve this
problem. According to a process of this kind, a material such as
novolac and polyimide that can be readily dry-etched by oxygen
plasma is deposited by spin coating on a substrate and planarized,
a resist resistant to dry etching by oxygen is applied to the
surface of the planarized layer, a pattern is formed, and then the
pattern is transferred to the bottom layer by anisotropic etching
by oxygen plasma. As this process yields patterns of a high aspect
ratio, developmental works are being conducted extensively on
resist materials resistant to oxygen plasma etching.
Resist materials utilizing silicone resins are known to be highly
resistant to oxygen plasma etching and, for example, compositions
consisting of ladder type polysiloxane esters or polysiloxanes
substituted with epoxy-containing alkyl groups and a photosensitive
compound capable of generating acid upon exposure to light are
proposed in JP 7-56354 (1995)A1 and JP 8-193167 (1996)A1. Moreover,
resist compositions containing photosensitive silicone resins that
are polysiloxanes to which a diazonaphthoquinonesulfonyloxy group
and an azido group are linked are proposed in JP 6-27671 (1994)A1
and JP 6-95385 (1994)A1.
As for the barrier (rib) of a plasma display panel (PDP), a process
for constructing a rib with the use of a paste formulated from
photosensitive resins and inorganic powders to raise the aspect
ratio is described in JP 10-62981 (1998)A1. The photosensitive
resins in question are acrylic polymers and the like.
Polyorganosilsesquioxanes are occasionally abbreviated to
polysiloxanes and they are known to occur in three types, that is,
cage, ladder, and random. Their structures and methods of
preparation are described in detail in the specifications of
WO98/41566, JP 50-139900 (1975)A1, JP 6-329687 (1994)A1, JP
6-248082 (1994)A1 and elsewhere. A method for introducing
functional groups to the ends of these polyorganosilsesquioxanes is
also described in detail in the aforementioned WO98/41566.
An object of this invention is to provide photosensitive silicone
resins which exhibit excellent performance as resist materials for
multi-level resist processes and for forming PDP barriers. Another
object of this invention is to provide resist materials which
exhibit excellent plasma resistance (resistance to O.sub.2 -RIE)
and form patterns of a high aspect ratio.
DISCLOSURE OF THE INVENTION
This invention relates to silicone resins composed of
polyorganosilsesquioxanes whose ends are partly or wholly linked to
a triorganosilyl group represented by the following general formula
(1) ##STR2##
(wherein R is a divalent organic group and R' is a divalent group
or a direct bond).
This invention also relates to the aforementioned silicone resins
wherein the polyorganosilsesquioxanes have a repeating unit
represented by the following general formula (2) ##STR3##
(wherein R.sub.2 is an unsubstituted or substituted phenyl group)
and the average number of repeating units is 2-5,000.
Furthermore, this invention relates to the aforementioned silicone
resins wherein the polyorganosilsesquioxanes consist of one type or
a mixture of two types or more selected from ladder type, cage
type, and mixed cage-ladder type and the weight average molecular
weight Mw is 800-100,000 as determined by gel permeation
chromatography (GPC) and calibrated against polystyrene.
Still more, this invention relates to the aforementioned silicone
resins wherein R is --R.sub.1 COOX.sub.1 -- or --R.sub.1 COOX.sub.1
--Si(CH.sub.3).sub.2 --O-- (wherein R.sub.1 is the divalent residue
of a polycarboxylic acid or derivative thereof and X.sub.1 is a
divalent group).
Still further, this invention relates to photosensitive resin
compositions formulated from the aforementioned silicone resins and
a photogenerator of acid.
Finally, this invention relates to a process for preparing the
aforementioned silicone resins which comprises treating
polyorganosilsesquioxanes with X--Si(R.sub.3).sub.2 --Y or
X--Si(R.sub.3).sub.2 OSi(R.sub.3).sub.2 --Y [wherein X and Y are
groups capable of linking with carboxyl groups or functional groups
capable of reacting with terminal OH groups or terminal OM groups
is an alkali metal) of the backbone of polyorganosilsesquioxanes
and R.sub.3 is a monovalent organic group] to give modified
polyorganosilsesquioxanes containing X or Y at all or a part of
their terminal positions, and treating the terminal groups with
t--BuOOC--R.sub.1 --COOH (wherein t--Bu is t-butyl group and
R.sub.1 is the divalent residue of a polycarboxylic acid or
derivative thereof). The group R.sub.3 here is a monovalent organic
group such as alkyl and aryl, preferably methyl, and R.sub.3 in a
given molecule may be of the same kind or of two or more kinds.
Photosensitive silicone resins of this invention are structurally
polyorganosilsesquioxanes to which a triorganosilyl group
represented by the aforementioned general formula (1) is linked to
all or a part of the ends of the backbone chain. The backbone chain
may be represented by the general formula (R.sub.2 Si.sub.2
O.sub.3).sub.n and n designates the number of repetition and is 2
or more. Preferable polyorganosilsesquioxanes have a repeating unit
represented by the aforementioned general formula (2) and the
average number of repeating units is 2-5,000, more preferably
5-500. The group R.sub.2 is a monovalent organic group and may be a
hydrocarbon group such as aryl and alkyl and an alkoxy group, but
R.sub.2 is preferably an alkyl group with 1-6 carbon atoms or an
unsubstituted or substituted phenyl group, more preferably a phenyl
group.
In the triorganosilyl group represented by the general formula (1),
R is a divalent organic group and, as indicated by the
aforementioned general formula (1), R may be said to contain the
residue of a carboxylic acid. The group R' designates a divalent
group or a direct bond and, in the case of a divalent group, it is
linked on the other side to the terminal Si--O-- group of
polyorganosilsesquioxanes. The t-butyl group at the end of of the
triorganosilyl group comes off to leave a free carboxyl group
behind when it contacts the acid generated from a photogenerator of
acid thereby enhancing the the alkali solubility of silicone resins
and it is this property that is utilized in patterning.
Carboxylic acids which give the divalent group R include
monocarboxylic acids such as benzoic acid and acetic acid and
polycarboxylic acids and they are preferably polycarboxylic acids.
Such polycarboxylic acids include pyromellitic acid, trimellitic
acid, phthalic acid, biphenyldicarboxylic acid,
biphenyltetracarboxylic acid, biphenylhexacarboxylic acid,
benzophenonedicarboxylic acid, benzophenonetetracarboxylic acid,
diphenyl ether dicarboxylic acid, diphenyl ether tetracarboxylic
acid, diphenyl sulfone dicarboxylic acid, diphenyl sulfone
tetracarboxylic acid, diphenyl sulfide dicarboxylic acid, diphenyl
sulfide tetracarboxylic acid, benzanilidedicarboxylic acid,
benzanilidetricarboxylic acid, benzanilidetetracarboxylic acid,
benzanilidepentacarboxylic acid, cyclohexanedicarboxylic acid,
cyclohexenedicarboxylic acid, succinic acid, adipic acid, maleic
acid, and fumaric acid.
In the case of polycarboxylic acids, the carboxyl group not linked
to t-butyl group may be present as free carboxyl (--COOH) or in the
form of ester or salt. In particular, it is preferable that one of
the carboxyl groups forms an ester linkage with Si either directly
or through a divalent group X as illustrated by t--Bu--OOC--R.sub.1
--COO--X--Si(Me).sub.2 --. Here, the group R in the general formula
(1) corresponds to R.sub.1 --COOX and X is a divalent group such as
alkylene or arylene or a direct bond.
In case polycarboxylic acids is tricarboxylic or higher acids, at
least one of the carboxyl groups remains intact and it may remain
so or it may be converted to the neutral form such as ester and
salt. Alkali solubility becomes poorer if the carboxyl group in
question exists in the neutral form such as ester. The acid from a
photogenerator of acid contributes to enhance alkali solubility by
dissociating the t-butyl group and generating a carboxylic acid. In
the cases in which patterning is effected by utilizing this
phenomenon, there should desirably be a large difference in alkali
solubility between the exposed and unexposed regions and, for this
reason, the free carboxyl groups are converted to esters,
preferably to t-butyl esters by treating with t-butyl alcohol or
derivative thereof.
The group R may contain not only the residue of a carboxylic acid
but also a part of the residue of a terminal modifier which
modifies the ends of polyorganosilsesquioxanes as described above.
A suitable terminal modifier can be represented by
X--Si(CH.sub.3).sub.2 --Y in which Y is a functional group capable
of linking to the backbone polyorganosilsesquioxanes and X is a
functional group capable of linking to a group such as carboxyl.
For example, a terminal modifier represented by
X--Si(CH.sub.3).sub.2 --O--Si(CH.sub.3).sub.2 --Y [wherein Y is a
functional group such as epoxy capable of reacting with the
terminal OH or OM group (M is an alkali metal)] reacts with
polyorganosilsesquioxanes at one end through Y to give
polyorganosilsesquioxanes containing X at the other end. The
X-terminated polyorganosilsesquioxanes then react with the
aforementioned polycarboxylic acid or derivative thereof to give a
product whose R contains --CH.sub.2 --CH(OH)-- in case X is an
epoxy group. A variety of groups such as ester and amide can be
formed by changing X. In the aforementioned terminal modifier, X
and Y may naturally be identical with or different from each other,
but one of them needs to be reactive with the terminal group (or
terminal group being generated during the reaction) of
polyorganosilsesquioxanes and the other needs to be reactive with a
group such as carboxyl or derivative thereof. As is apparent from
the above description, the backbone polyorganosilsesquioxanes and
the triorganosilyl group represented by the general formula (1) are
linked not necessarily through a siloxane linkage but through an
appropriate group.
Photosensitive silicone resins of this invention can be prepared by
utilizing a known reaction. In the case of
polyorganosilsesquioxanes containing terminal silanol, for example,
the terminal modification is effected by treating the polymers with
a monohalide such as X--Si(CH.sub.3).sub.2 --Cl. One of preferable
procedures for terminal modification is to treat
polyorganosilsesquioxanes such as silanol-free cage type and/or
ladder type octaphenylsesquioxane with a terminal modifier such as
the aforementioned X--Si(R.sub.3).sub.2 --O--Si(R.sub.3).sub.2 --X
in the presence of an alkali metal catalyst to give X-terminated
polyorganosilsesquioxanes.
A silicon atom in polyorganosilsesquioxanes and the silicon atom in
a terminal modifier such as X--Si(CH.sub.3).sub.2 --Y tend to
undergo exchange reaction and a procedure utilizing this property
is also effective for terminal modification. In this case, at least
one of X and Y needs to be reactive with a carboxyl group.
Moreover, it is possible to effect the aforementioned reaction and
the exchange reaction simultaneously by using Y as a group capable
of reacting with the end of polyorganosilsesquioxanes.
A preferable procedure for preparing silicone resins of this
invention from terminally modified polyorganosilsesquioxanes is,
for example, to treat the terminally modified
polyorganosilsesquioxanes with an acidic ester prepared by the
reaction of t-butyl alcohol with a polycarboxylic acid or
derivative thereof such as acid anhydride in the presence of a
quaternary ammonium salt as a catalyst.
Silicone resins of this invention have a weight average molecular
weight of 800-100,000, preferably 5,000-50,000, as determined by
GPC and calibrated against polystyrene. The silicone resins in
question are solid at normal temperature and soluble in many
organic solvents such as esters and ethers. Furthermore, silicone
resins of this invention are preferably polyorganosiloxanes
represented by the general formula (C.sub.6 H.sub.5
S.sub.3/2).sub.n having a triorganosilyl group represented by the
general formula (1) at all or 10% or more of their replaceable
ends, for example, one triorganosilyl group for n=4-20, preferably
one for n=2-8.
Silicone resins of this invention are best suited for use as
positive resist materials. In such end uses, it is possible to
incorporate generators of acid or a variety of additives in order
to enhance sensitivity or improve heat or a plasma resistance.
Additives indispensable to photosensitive resin compositions of
this invention are photogenerators of acid. Such photogenerators of
acid include, but are not limited to, sulfonium salts such as
triphenylsulfonium trifluorosulfonate, triphenylsulfonium
trifluoromethaneantimonate, triphenylsulfonium benzenesulfonate,
and cyclohexylmethyl(2-oxocyclohexyl)sulfonium
trifluoromethanesulfonate, iodonium compounds such as
diphenyliodonium trifluoromethanesulfonate, and
N-hydroxysuccinimide trifluoromethanesulfonate. A detailed
description of the chemical formulas and actions of these
photogenerators of acid is found in the aforementioned JP 8-193167
(1996)A1 and "New Development of Practical Polymer Resist
Materials", p. 57 (in Japanese) published by CMC. A photogenerator
of acid is normally added at a rate of 0.2-25% by weight of total
solids.
An organic solvent is used to adjust the viscosity. Preferable
solvents include, but are not limited to, Methyl Cellosolve
acetate, propylene glycol monoethyl ether acetate, methyl lactate,
ethoxyethyl acetate, methyl pyruvate, methyl methoxypropionate,
N-methylpyrrolidinone, cyclohexanone, methyl ethyl ketone, dioxane,
ethylene glycol monomethyl ether acetate, and diethylene glycol
monoethyl ether.
Photosensitive resin compositions of this invention contain the
aforementioned photosensitive silicone resins and photogenerators
of acid as indispensable components and often contain solvents. In
addition, it is permissible to incorporate surfactants, colorants,
stabilizers, coating improvers, and inorganic powders as
needed.
Photosensitive silicone resins of this invention and their
compositions can be used as resist materials and barrier materials
of PDP. Although there is no restriction on the mode of their use
as resist material, they are best suited for multi-level resist
processes.
According to a multi-level resist process, a material such as
novolac which can be readily dry-etched by oxygen plasma is applied
by spin coating to the surfaceof a substrate, a material of this
invention is applied thereto, the layers are exposed to a laser
such as excimer to generate acid from a photogenerator of acid and
let the acid dissociate silicone resins, patterning is effected by
developing with an aqueous alkaline solution, and the bottom layer
resist is etched by oxygen plasma to give a pattern of a high
aspect ratio.
As for the preparation of barrier materials of PDP, methods such as
sandblasting, embedding, and photopaste are known. Since any of the
methods uses photosensitive resist materials, materials of this
inventin can be used as such. In particular, when applied to the
photopaste method or the like in which the resist remains
unremoved, materials of this invention can fully produce the effect
of excellent plasma resistance.
PREFERRED EMBODIMENTS OF THE INVENTION
Example 1
Phenylsilsesquioxane containg glycidyl group was synthesized with
reference to Reference Example 1 and Example 3 described in
PCT/JP98/01098 (WO98/41566) and JP 10-251407 (1998)A1.
Synthetic Example 1
Synthesis of Cage Type Octaphenylsilsesquioxane
In 500 cc of toluene was dissolved 105 g (0.5 mole) of
phenyltrichlorosilane and the mixture was shaken with water until
the hydrolysis was completed. The hydrolysis product was washed
with water, mixed with 16.6 cc (0.03 mole) of commercially
available 30% methanol solution of benzyltrimethylammonium
hydroxide, and the mixture was heated at reflux temperature for 4
hr.
Thereafter, the whole mixture was cooled and left standing for
approximately 96 hr. After this time elapsed, the resulting slurry
was again heated at reflux temperature for 24 hr, cooled, and
filtered to give about 75 g of cage type octaphenylsilsesquioxane
(C.sub.6 H.sub.5 SiO.sub.3/2).sub.8. In infrared spectrometry of
the product, absorption bands assignable to Si--C.sub.6 H.sub.5
were observed at 1595 cm.sup.-1 and 1430 cm.sup.-1 and an
absorption band assignable to the antisymmetric stretching
vibration of Si--O--Si was observed at 1135 cm.sup.-1 while an
absorption band assignable to Si--OH was not observed at 3400
cm.sup.-1. In .sup.29 Si-MASNMR determination, only one sharp
signal of Si nucleus in the cage type octaphenylsilsesquioxane was
observed at -77 ppm. The number average molecular weight Mn was 760
when determined by GPC with o-dichlorobenzene used as a flowing
solvent and calibrated against polystyrene.
Synthetic Example 2
Synthesis of Phenylsilsesquioxane Oligomer Containing Glycidyl
Group
To a reaction vessel were added 100 g of the cage type
octaphenylsilsesquioxane, 70.3 g of
1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane, 400 g of
toluene, and 4 g of tetramethylammonium hydroxide pentahydrate and
the mixture was heated at reflux temperature with vigorous stirring
for 7 hr. The reaction mixture was a white suspension at the start
because white powders of the the cage type octaphenylsilsesquioxane
did not dissolve in toluene, but the powders gradually dissolved as
the reaction progressed and nearly all of them dissolved after 7 hr
to give a colorless transparent solution. The solution was cooled
to room temperature, a precipitate of the unreacted
tetramethylammonium hydroxide was removed by filtration, and the
filtrate was poured into 2,000 g of excess methanol to
reprecipitate phenylsilsesquioxane containing a terminal glycidoxy
group. The viscous precipitate was washed with methanol and
distilled to strip off the methanol and the residual toluene to
give 120 g of glycidyl-containing phenylsilsesquioxane oligomer as
a pale yellow transparent viscous product. The epoxy equivalent as
determined by the hydrochloric acid-pyridine method was 945 g/eq.
The number average molecular weight Mn determined by GPC and
calibrated against polystyrene was 20,000.
Synthetic Example 3
Synthesis of Carboxylic Acid Containing t-Butyl Ester Group
To a 1-l three-necked flask were added 62 g of maleic anhydride, 74
g of sodium t-butoxide, and 400 g of propylene glycol monomethyl
ether acetate, 0.44 g of sodium methoxide was added as a catalyst,
and the mixture was heated under reflux at 150.degree. C. for 2 hr.
The mixture was allowed to cool to room temperature and 0.85 g of
concentrated hydrochloric acid was added. The resulting brown
reaction mixture was placed in an eggplant-shaped flask and the
solvent propylene glycol monomethyl ether acetate was distilled off
in an evaporator. Thereafter, the remainder was dissolved in 600 of
dichloromethane andwashed with 500 g of distilled water three
times. The dichloromethane was evaporated off to give a carboxylic
acid containing a t-butyl ester group as a brown viscous liquid in
90% yield.
Synthetic Example 4
Synthesis of Phenylsilsesquioxane Containing t-Butyl Ester
Group
To a three-necked flask were added 100 g of the glycidyl-containing
phenylsilsesquioxane oligomer prepared in Synthetic Example 2, 14 g
of the carboxylic acid containing a t-butyl ester group prepared in
Synthetic Example 3, 100 g of propylene glycol monomethyl ether
acetate as a solvent, and 0.2 g of tetraethylammonium bromide as a
catalyst and the mixture was heated at 90.degree. C. with stirring
for 2 hr to give phenylsilsesquioxane containing a t-butyl ester
group as a brown viscous liquid in 80% yield.
Example 2
(1) Experiments on Pattering Using Resins of this Invention
A photosensitive resin solution was prepared by dissolving 1 g of
triphenylsulfonium triflate (Ph.sub.3 S.sup.+ OTf.sup.-) or a
photogenerator of acid in 100 g of a solution of the
phenylsilsesquioxane containing t-butyl ester group prepared in
Example 1 in propylene glycol monomethyl ether acetate and the
solution was applied by spin coating to a glass substrate and dried
at 70.degree. C. for 15 minutes to form a 0.3 .mu.m-thick film. The
film was irradiated with UV (248 nm) through a mask and developed
by a 3% aqueous solution of tetramethylammonium hydroxide to give a
clear pattern (line and space 0.3 .mu.m). It was confirmed that the
resin exhibits a property of positive resist.
(2) Experiments on Two-level Resist Patterning Using Resins of this
Invention
A silicon wafer was spin-coated with a 1 a m-thick bottom resist
layer of cresol novolac and a 0.1 .mu.m-thick top positive resist
layer of the phenylsilsesquioxane containing t-butyl ester group
prepared in Example 1, exposed to far UV (193 nm) excimer laser,
and developed with a 2% aqueous solution of tetramethylammonium
hydroxide to form a dear pattern in the top layer (line and space
0.1 .mu.m). Thereafter, the bottom resist was etched by O.sub.2
--RIE and the top resist was removed by CF.sub.4 --RIE to form
clearly patterned cresol novolac with a linewidth of 0.1 .mu.m and
an aspect ratio of 10.
Industrial Applicability
Silicone resins of this invention and their compositions give
resists of excellent plasma resistance and make precision
patterning of electronic devices feasible. They are also well
suited for barrier materials of PDP and, moreover, exhibit
excellent performance as resist materials for multi-level resist
processes and for forming barriers of PDP. In addition, they
exhibit excellent plasma resistance (resistance to O.sub.2 -RIE)
and, when used in patterning, give patterns of a high aspect
ratio.
* * * * *